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Titan glows in the dark

This set of images from NASA’s Cassini spacecraft shows Saturn’s moon Titan glowing in the dark. Titan was behind Saturn at the time, in eclipse from the sun. The image on the left is a calibrated, but unprocessed image from Cassini’s imaging camera. The image on the right was processed to exclude reflected light off Saturn and it is clear that even where Titan did not receive any Saturnshine, it is still emitting light.

A literal shot in the dark by imaging cameras on NASA’s Cassini spacecraft has yielded an image of a visible glow from Titan, emanating not just from the top of Titan’s atmosphere, but also – surprisingly – from deep in the atmosphere through the moon’s haze.

“It turns out that Titan glows in the dark – though very dimly,” said Robert West, the lead author of a recent study in the journal Geophysical Research Letters and a Cassini imaging team scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “It’s a little like a neon sign, where electrons generated by electrical power bang into neon atoms and cause them to glow. Here we’re looking at light emitted when charged particles bang into nitrogen molecules in Titan’s atmosphere.”

Scientists are interested in studying the input of energy from the sun and charged particles into Titan’s atmosphere because it is at the heart of the natural organic chemistry factory that exists in Titan’s atmosphere.

The scientists took into account sunlight reflected off Saturn. There was still a glow from the part of Titan that was dark. The luminescence was diffusing up from too deep for charged particles from the sun to be exciting atmospheric particles. The area was also not affected by the shooting of charged particles into the magnetic fields, which is what causes auroras.

Scientists’ best guess is that the glow is being caused by deeper-penetrating cosmic rays or by light emitted due to some kind of chemical reaction deep in the atmosphere.